The present invention relates to a light-sensitive material production method wherein a curtain coater is used to manufacture light-sensitive materials through stable curtain coating.
There has been known a method for manufacturing light-sensitive materials by the use of a curtain coater wherein a coating solution in a form of a uniform layer flowing down along a slide surface of a coater die is caused to fall from a tip of a die lip of the coater die to be formed into a thin curtain layer of coating solution which is, then, put continuously on a web of a long support to be coated thereon, while the support is running at a certain high speed. In a method for manufacturing light-sensitive materials by the use of the curtain coater mentioned above, it is very important that a curtain layer is formed in a stable manner. When the coating solution flowing down along the slide surface leaves the die lip to be formed into a curtain layer, the coating solution whose surface tension makes it to shrink is held by a bar (or a plate) located at the side and called an edge guide so that a width of the curtain layer may be secured. However, when the edge guide fails to resist a force of the coating solution to shrink, a broken curtain layer is caused, making it difficult to form a curtain layer in a stable manner. In a prior art, there happened frequently phenomena wherein a curtain layer has been broken without being formed, or, even if it is formed, a curtain layer on the side edge is broken simultaneously with the start of coating by a force with which a coating solution is pulled in the direction of conveyance of a support, due to a lack of a force of the edge guide to support the curtain layer. For eliminating these phenomena, there have been made various proposals.
Namely, Japanese Patent Publication Open to Public Inspection No. 99668/1989 (hereinafter referred to as Japanese Patent O.P.I. Publication) discloses a means to strengthen and stabilize a curtain layer by causing side solutions to flow additionally on end portions at both sides for improving the foregoing by preventing the broken curtain layer. In this means, however, the side solution is accumulated on each end portion intensively, resulting in an excessively thick layer on each of both sides, although the curtain layer is not broken.
For the intent of inhibiting the increase in a layer thickness on each side, coating solutions on a thick layer portion on an end portion of a curtain layer at the edge guide section are removed through suction, as disclosed in Japanese Patent O.P.I. Publication Nos. 477/1986 and 233954/1994.
In Japanese Patent O.P.I. Publication No. 57734/1976, curtain layer is stabilized by the use of an edge guide of a flat plate type. However, even in this case, a curtain layer can not be stabilized, and some types of coating solutions make it impossible to form a curtain layer. A problem of the phenomenon that both edges of a curtain layer are caused to be thick can not be solved either.
As stated above, various types of coating apparatuses have been proposed so far for forming a curtain layer, but none of them is satisfactory.